To be honest, pointing this out isn't really a smooth move. I mean, you didn't say anything explicitly but you're still giving people the wrong idea - that it's a "thing" for people to "use" a "condition" to express how they have "NO CONTROL". Isn't that a bit critical for those of us who have to deal with being overweight? Like, how am I supposed to react to that? Yaay, /thread? Yaay, valid point? There's a huge grey area between recognizing your genetic hindrances and outright offloading all responsibility onto it, yet you're going really hard with that comment.
Like the OP said, this is about stigmatization and shaming. You can be fat and ashamed of yourself, and you can be fat and confident in yourself. In which scenario would you imagine the hypothetical person to actually do something? Comments like yours pop up a million time over in these threads, but I never manage to read anything positive. This usually turns into a pissing match in which people affected by being overweight talk about their challenges. When you boil it down, it's a stupid argument between people believing they have legitimate obstacles and people believing these obstacles are not worthy - it turns into an argument of judgment and appraisal, which isn't constructive. You can make it an issue about choice, but there honestly isn't much, and much useful talk that comes out of that.
It'd be nice if we could hear something about, I dunno, how to encourage those that are affected by fat shaming and generalizations to move past all the negative. The reason anyone would fall into frustration and depression isn't because they don't know their problem enough, it's because they know their problem too darn well. If you want to do something in life, you need motivation and encouragement and that goes for everything. You can point out a problem, or you can point out how to solve it - which isn't hard if you look a little inside yourself, for we all have faced and overcame adversity in some way.